stderr has expected failure message

Author: mdeuser

tests/src/test/scala/org/apache/openwhisk/core/cli/test/WskCliBasicUsageTests.scala

@@ -1574,7 +1574,7 @@ class WskCliBasicUsageTests extends TestHelpers with WskTestHelpers {
 
     try {
       wsk.trigger.create(triggerName, feed = Some(actionName), parameters = feedActionCreateParams)
-      wsk.trigger.delete(triggerName, expectedExitCode = ERROR_EXIT).stdout should include(
+      wsk.trigger.delete(triggerName, expectedExitCode = ERROR_EXIT).stderr should include(
         """Unable to delete trigger""")
     } finally {
       wsk.cli(